LEDs (Light Emitting Diodes), especially high brightness LEDs, may be used as flash light sources to illuminate scenes for photography or videography. When used for flash photography these LEDs may operate by converting very high currents from a current source into white light for very brief periods of time, for example, on the order of a few hundred milliseconds or less. The ability to control the variance of the high current accuracy with a small compliance voltage across the current source may be critical for power efficiency when used in battery driven applications.
A traditional current source is required to produce a large current, but there may be a desire to minimize the losses in producing this large current by reducing the voltage drop across a driving transistor and an output resistor. This leads to a very low resistance output resistor that becomes very expensive to achieve the required accuracy of the resistance value. Further, such a current source will have large variations due to changes in temperature. These challenges make it difficult and expensive to try to produce a high precision high current with such a current source.